Student Projects
Prospective students may propose projects in agreement with a core team member or other supervisor. The project outlines below are simply guidelines to projects of particular interest to core team members. Please contact the responsible core team member for further details.
Click on a project title in the list below to view its details

Project summary list

Project title Level
1. Determining a risk assessment for cultivars of alien plant invaders PhD
2. Earthworms as threats and opportunities in South Africa: building capacity to understand the costs and benefits PhD
3. The social dimensions of river management: a case study of the Eerste River MA
4. Exploring the invasion of Guttural Toads (Amietophrynus gutturalis) MSc and/or PhD
5. The three-threshold model — a conceptual framework applied — implications for improved management of invasive Acacia species MSc
6. Assessing invasive alien plant impacts on ecosystem services on the City of Cape Town MSc
7. Pro-active management of biological invasions in the City of Cape Town MSc
8. Identification of priority areas for restoration MSc
9. Ecological impacts of the white garden snail (Theba pisana) MSc or PhD
10. Biodiversity impacts of plant invasions — the role of mutualisms MSc, PhD or Postdoc
11. Propagule pressure: The role of forestry plantations MSc, PhD or Postdoc
12. The tale of two island endemics, Acacia koa and A. heterophylla PhD
13. The architecture of pollination and seed-dispersal networks of Australian acacias PhD or Post-Doc
14. From snapshots of species distribution to landscape-scale dynamics of invasive plants MSc or Post-Doc
15. Seed dispersal and spread potential of invasive Australian acacias PhD or Post-Doc
16. Identifying key species characteristics underpinning successful invasion of the ladybird Cryptolaemus montrouzeri: a multidisciplinary approach MSc
17. Bamboo cultivation in South Africa – an assessment of the potential impacts and developing guidelines for cultivation best practices MSc
18. The invasion ecology of fleshy-fruited Myrtaceae, with special emphasis on South Africa MSc or PhD
19. An assessment of the extent of invasion and genetic structure of Eucalyptus camaldulensis in South Africa MSc
20. Risk assessment of introduced alien grasses in South Africa Honours or MSc

Core Team Members: Dr John Wilson, Centre for Invasion Biology, Stellenbosch University

Level of project: PhD

Working title: Determining a risk assessment for cultivars of alien plant invaders

Background

The movement of plants around the world by the horticultural trade has historically been one of the major proximate causes of biological invasions. Legislation is currently being amended in South Africa as part of the National Environmental Management: Biodiversity Act to restrict the use of and trade in species that pose a high invasion risk to South Africa. One recommendation is that cultivars of species listed as invasive (or potentially invasive) that have an acceptable invasion risk (e.g. through sterility) are explicitly specified in and exempt from the regulations.

The purpose of the studentship would be to develop tests that are necessary and sufficient to allow the cultivation of plants that would otherwise be regulated under NEM:BA. This would involve experimental tests of particular cultivars, an in-depth analysis in a particular group, and the development of a risk assessment protocol. They would also potentially shed light on species boundaries in plants. As such it is expected to produce both practical guidelines, and evolutionary insights that are publishable in top international journals. The project has the potential to link with the Early Detection and Rapid Response program of SANBI.

This is a project suitable for students interested in molecular biology, evolutionary biology, ecology, and horticulture.

Key contacts

  • Dr John Wilson, South African National Biodiversity Institute / Centre for Invasion Biology, Stellenbosch University (jrwilson@sun.ac.za)
  • Dr Jaco Le Roux, Centre for Invasion Biology, Stellenbosch University (jleroux@sun.ac.za)
  • Prof David Richardson, Centre for Invasion Biology, Stellenbosch University

Further reading:

  • Dehnen-Schmutz K, Touza J, Perrings C and Williamson M (2007) A century of the ornamental plant trade and its impact on invasion success. Diversity and Distributions 13: 527-534
  • Pemberton RW and Liu H (2009) Marketing time predicts naturalization of horticultural plants. Ecology 90: 69-80
  • Reichard SH and White P (2001) Horticulture as a pathway of invasive plant introductions in the United States. BioScience 51: 103-113
  • Wilson RL and Hoch WA (2009) Identification of Sterile, Noninvasive Cultivars of Japanese Spirea. HortScience 44: 2031-2034

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Core Team Members: Dr John Wilson, Centre for Invasion Biology, Stellenbosch University

Level of project: PhD (x3 based at UKZN or Stellenbosch University)

Working title: Earthworms as threats and opportunities in South Africa: building capacity to understand the costs and benefits

Background

Earthworms play a major role as ecosystem engineers in both natural and agricultural systems. They are also increasingly being used for soil improvement, composting, waste disposal, and as bait for angling. However there has been no scientific assessment of whether these uses pose a risk to South African biodiversity. Moreover, South Africa is known to have a unique earthworm fauna which is yet to be fully documented, and as such building capacity to conduct earthworm research over the medium term is an urgent priority for natural resource management.

The first two PhD projects will involve assessments of the diversity and distribution of native and alien earthworms in several threatened biomes: fynbos, Afro-montane forest, grassland & savanna. This research will include detailed surveys of earthworms in landscape scale transects moving across land-use types including urban, peri-urban, agricultural and natural systems in two regions of South Africa: the Cape Floristic Region and in KwaZulu-Natal.

The third PhD will involve an assessment of the introduction of and trade in earthworms in South Africa. This work will assess which earthworms are currently being actively used in South Africa and appraise introduction routes (both deliberate and accidental) and current introduction rates by taking samples from vermiculture and other relevant industries (e.g. soil in potted plants used in horticulture). It will include an in-depth study of domestic vermicomposting (samples in gardens with different users who have practised vermicomposting over different number of years) and explore the socio-economic drivers of the industry. In collaboration with local authorities and stake-holders the project will produce guidelines for the public.

Key contacts

  • Dr. Sandi Willows-Munro, University of KwaZulu-Natal, (willows-munro@ukzn.ac.za)
  • Dr John Wilson, South African National Biodiversity Institute / Centre for Invasion Biology, Stellenbosch University (jrwilson@sun.ac.za)

Further reading:

  • Copley, J. (2000) Ecology goes underground. Nature, 406, 452-454.
  • Hendrix, P. F., Callaham, M. A., Drake, J. M., Huang, C. Y., James, S. W., Snyder, B. A. & Zhang, W. X. (2008) Pandora's Box contained bait: the global problem of introduced earthworms. Annual Review of Ecology Evolution and Systematics, 39, 593-613.
  • Lavelle, P., Decaens, T., Aubert, M., Barot, S., Blouin, M., Bureau, F., Margerie, P., Mora, P. & Rossi, J. P. (2006) Soil invertebrates and ecosystem services. European Journal of Soil Biology, 42, S3-S15.
  • Plisko, J. D. (2010). Megadrile earthworm taxa introduced to South African soils (Oligochaeta: Acanthodrilidae, Eudrilidae, Glossoscolecidae, Lumbricidae, Megascolecidae, Ocnerodrilidae). African Invertebrates 51, 289–312.
  • Wardle, D. A., Bardgett, R. D., Klironomos, J. N., Setala, H., van der Putten, W. H. & Wall, D. H. (2004) Ecological linkages between aboveground and belowground biota. Science, 304, 1629-1633.

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Core Team Members: Dr Heidi Prozesky, John Wilson, Dave Richardson

Level of project: MA

Working title: The social dimensions of river management: a case study of the Eerste River

Background

Invasive species are ultimately the result of human choices and actions, and humans have an important role to play (whether accidentally or intentionally) in determining which species grow where. As such, biodiversity value, particularly that of transformed environments, is a function of social variables. More directly, the ability to manage, for example, a river (including its water flow rates and flood prevention) is determined by how people view biodiversity. Students interested in social attitudes towards IAS could join students and staff at the DST-NRF Centre of Excellence for Invasion Biology in a long-term inter-disciplinary project on the management of “Stellenbosch University's River&rdquo, the Eerste River. This would imply linking their research to a a longitudinal case study of the changing stresses upon the river system, with a particular focus on an invasive alien plant, Acacia implexa. As changes in stresses are highly dependent on changes in attitudes and actions of the people who interact (whether intentionally or accidentally) with the river system, it is necessary to complement the time series of the biological data with social research aimed at answering questions such as the following: Which species are people growing, and how do they view the effect of their actions? How do they view efforts to control or manage particular species? What function they want the river to serve? Do they know the ecological state of the river? The student will therefore be expected to collect base-line data on people's perceptions and usage of the water-way, to allow for on-going assessments of changes in such orientations and behaviour. Ultimately, the research should also be aimed at informing practical management and to demonstrate potential, tangible actions related to the eradication of Acacia implexa.

Key contacts

  • Dr Heidi Prozesky, Centre for Invasion Biology, Stellenbosch University (hep@sun.ac.za)

Further reading:

  • Meek, C. S., Richardson, D. M. & Mucina, L. (2010) A river runs through it: Effects of land use on alien plant composition along a riparian corridor in the Cape Floristic Region, South Africa. Conservation Biology, 143, 156-164.
  • Simberloff, D. (2009) We can eliminate invasions or live with them: successful management projects. Biological Invasions, 11, 149–157.
  • García-Llorente, M., Martín-López, B., González, J. A., Alcorlo, P. & Montes, C. 2008. Social perceptions of the impacts and benefits of invasive alien species: implications for management. Biological Conservation 141, 2969-2983.
  • Kaiser, F. G. , Wölfing, S. & Fuhrer, U. (1999). Environmental Attitude and Ecological Behaviour. Journal of Environmental Psychology, 19, 1-19.
  • Hunter, L. M. & Brehm, J. (2003) Qualitative insight into public knowledge of, and concern with, biodiversity. Human Ecology, 31, 309-320.

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Core Team Members: Sarah Davies, Centre for Invasion Biology, Stellenbosch University

Associate: John Measey, Department of Zoology, Nelson Mandela Metropolitan University

Level of project: Masters and/or PhD

Working title: Exploring the invasion of Guttural Toads (Amietophrynus gutturalis)

Background

‘Domestic exotics’ are species that have invaded areas within national boundaries (Guo & Ricklefs 2010). Although such species are potentially just as threatening as internationally travelling invasive species, they often go unnoticed or are ignored due to their presence in national guides. A recent review found that the number of domestic exotics is generally underestimated as many are regularly considered ‘native’. Further, domestic exotics are likely to increase, because the drivers of their introduction and spread are becoming more prominent, among them the pet and cargo/nursery trades (Kraus 2009), extensive landscape change (Davies et al 2013) and climate change. We ignore these species at our peril as has been shown for amphibian species introduced to the Western Cape Province of South Africa (Measey & Davies 2011).

The guttural toad (Amietophrynus gutturalis) has been in Cape Town since 2000. The toads are presumed to have been accidentally introduced from another part of South Africa (possibly Durban) as eggs or tadpoles with a consignment of aquatic plants (de Villiers 2006). This area is within the range of the Endangered western leopard toad (Amietophrynus pantherinus), raising concerns about the effects of the invasion on this species. In addition, the guttural toad has been introduced to Reunion (1927) and Mauritius (1922) as a biological control agent, where it has been blamed (together with shrews and tenrecs), for devastating native snail populations.

In 2006 guttural toads were restricted to an area of less than 2 km2 around the presumed site of introduction. An attempt was made to eradicate this population in 2003, and 30 adult toads were removed from the site, but the operation floundered due to a lack of resources and sustained effort. By 2008, the guttural toad population was still spreading and a decision was made by the CAPE Invasive Alien Animal Working Group (CAPE-IAA) to mount a sustained eradication campaign. By the end of 2009, captures, calls and sightings revealed that the distribution covered approximately 10 km2 (City of Cape Town Biodiversity Management, unpublished data). The CAPE-IAA has secured funding to continue this campaign and to date 1 835 guttural toads, plus eggs and tadpoles, have been removed.

This project will compare the reproductive biology and growth rates of invasive guttural toads in Cape Town from those in their native range (Mpumalanga/Limpopo); and/or studies on morphological adaptations and the expansion of the population using population genetics.

Key contacts

Interested candidates should send applications by email to John Measey (john.measey@nmmu.ac.za) or Sarah Davies (sdavies@sun.ac.za). See http://john.measey.com/ for additional information.

Applications should include a cover letter stating motivation for doing the project, an updated academic CV including exam transcripts and contact information (telephone and email) of two referees.

Further reading

  • Davies, S. J., Clusella-Trullas, S., Hui, C., & McGeoch, M. A. (2013). Farm dams facilitate amphibian invasion: Extra-limital range expansion of the painted reed frog in South Africa. Austral Ecology.
  • Measey, G. J., & Davies, S. J. (2011). Struggling against domestic exotics at the southern end of Africa. FrogLog, 97, 28-30.
  • Measey, G. J., Rödder, D., Green, S. L., Kobayashi, R., Lillo, F., Lobos, G., ... & Thirion, J. M. (2012). Ongoing invasions of the African clawed frog, Xenopus laevis: a global review. Biological Invasions, 14, 2255-2270.

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Core Team Members: Mirijam Gaertner, Stellenbosch University

Level of project: MSc

Working title: The three-threshold model — a conceptual framework applied — implications for improved management of invasive Acacia species

Background

Several of the most widespread and damaging invasive plant species in South Africa are from the genus Acacia. Australian Acacias have a huge invasion potential and a wide range of impacts on the native ecosystem. Effects of invasive Acacia species on biotic and abiotic components of South African fynbos ecosystems have been studied extensively. Recently it has been suggested that ecosystem changes following invasion result in ecosystem thresholds (tipping points) at which reinforcing feedback mechanisms further facilitate the invader. The processes that underlie these feedback mechanisms have been studied for certain ecosystem components (e.g. soil seed bank and soil nutrient cycling) but have not been extensively explored for others (e.g. soil moisture regimes/water resources). At the same time the concept of ecosystem thresholds has so far only been described in theory but has not been tested empirically.

The objective of this study is to conduct vegetation and soil surveys along a gradient of Acacia invasion and across a climatic gradient in lowland fynbos ecosystems to identify abundance thresholds (tipping points) at which ecosystems change and effects on ecosystem services (in particular water resources) increase disproportionately. An improved understanding of ecosystem thresholds and related feedback mechanisms underlying Acacia invasion is crucial as a basis for managing and restoring native ecosystems. The results of this study will provide clear guidelines to enhance management strategies to reduce the negative impacts of invasions on biodiversity and ecosystem function.

The MSc project will be embedded in an extensive research program on ecosystem thresholds and is funded through the collaborative agreement between the Working for Water Program and the C·I·B. It is suitable for students who are interested in invasion biology and restoration ecology and who are happy to spend extended periods of time doing field work.

Key contacts

  • Dr Mirijam Gaertner, Centre for Invasion Biology (C·I·B) (gaertnem@sun.ac.za)
  • Prof Karen Esler, Department for Conversation Ecology and Entomology (ConsEnt) (kje@sun.ac.za)
  • Dr Shayne Jacobs, Department for Conversation Ecology and Entomology (ConsEnt) (sjacobs@sun.ac.za)

Further reading

  • Gaertner M, Holmes PM, Richardson DM. 2012. Biological invasions, resilience and restoration. Pages 265-280 in Andel J, Aronson J, eds. Restoration Ecology: The new frontier. Oxford: Wiley-Blackwell.
  • Le Maitre DC, et al. 2011. Impacts of invasive Australian acacias: Implications for management and restoration. Diversity & Distributions 17: 1015-1029.
  • Marchante E, Kjoller A, Struwe S, Freitas H. 2008. Short- and long-term impacts of Acacia longifolia invasion on the belowground processes of a Mediterranean coastal dune ecosystem. Applied Soil Ecology 40: 210-217.
  • Richardson DM, Kluge RL. 2008. Seed banks of invasive Australian Acacia species in South Africa: Role in invasiveness and options for management. Perspectives in Plant Ecology, Evolution and Systematics 10: 161-177.

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Core Team Members: Mirijam Gaertner, Stellenbosch University

Level of project: MSc

Working title: Assessing invasive alien plant impacts on ecosystem services on the City of Cape Town

Background

South Africa, like many other developing countries in Africa, is rapidly urbanizing. This poses a number of challenges both in terms of planning and service delivery. The role that ecosystem service provision plays in meeting services needs and benefits is gaining increasing attention and interest. There are however a number of drivers and pressures relating to ecosystem change and degradation that impact on the provision of ecosystem services. Invasive alien plant species are a major driver of ecological degradation in South Africa and considerable work has been done to improve our understanding of this issue and in turn inform their effective management. The effect that invasive alien plants have on ecosystem service provision within cities has however received little attention. We have limited understanding of which services are affected and how the underlying ecological function and mechanisms are altered by invasive alien species. Furthermore which species or which functional groups are having the greatest effects on particular services is currently unknown. If we are to meet current and future needs, then a fuller understanding of these disruptive processes and drivers is required.

This interdisciplinary M.Sc. level study will assess how different invasive plant species and functional groups of species affect the provision of services within the City of Cape Town. Here provisioning, regulating and cultural services will be examined and contrasted using a range of approaches and assessment techniques. These are likely to vary from detailed ecosystem function measurements to social assessments tackling issues relating to human resources use and benefits. Fieldwork measurements will be required as well as detailed analysis in exploring impacts relating to both the ecology within and out of the city. All components of the study will be developed in conjunction with the student.

The study forms part of a newly established collaboration between the Centre for Invasion Biology and the City of Cape Town Invasive Species Unit and is funded through the collaborative agreement between the Working for Water Program and the C·I·B.

This project would meet the interest of someone looking to expand their spatial analysis, social analysis and ecological fieldwork skills. Only students who attain 65% and above for their Honours year studies will be considered.

Key contacts

Further reading

  • O'Farrell PJ, Anderson PML, Le Maitre DC, Holmes PM. 2012. Insights and opportunities offered by a rapid ecosystem service assessment in promoting a conservation agenda in an urban biodiversity hotspot. Ecology and Society 17: 27.
  • Pejchar L, Mooney HA. 2009. Invasive species, ecosystem services and human well-being. Trends in Ecology & Evolution 24: 497-504.
  • Vilà M, et al. 2009. How well do we understand the impacts of alien species on ecosystem services? A pan-European, cross-taxa assessment. Frontiers in Ecology And The Environment 8: 135-144.

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Core Team Members: Mirijam Gaertner, Stellenbosch University

Level of project: MSc

Working title: Pro-active management of biological invasions in the City of Cape Town

Background

Preventing the introduction of invasive species is the first line of defence against invasions. However, even the best prevention efforts will not stop all invasive species being introduced. Most management only focusses on widespread invaders, but it is often much more cost-effective to treat problems proactively. This requires an early detection and rapid response (EDRR) type approach. EDRR efforts increase the likelihood that invasions can be successfully contained and populations removed while they are still small and the species distribution is still limited. Additionally detection of an invasive species while the population is relatively small can significantly reduce the cost of its eradication. With limited funds and resources available for invasive plant management, it becomes important to prioritise efforts based on the environmental and economic risks a species poses. An assessment of invasiveness and feasibility of eradication, based on a species' biology and population dynamics, will provide a good indication of the risk posed by a species and inform plans for the species' management.

The objective of this study is to assess the threats posed and management options for species that have been identified as priority species for early detection and rapid response by the Cape Town Invasive Species Unit. Specific aims are an initial assessment to determine the invasive potential of these species and whether eradication is still feasible. Additionally the study aims at testing different control methods for these species and to develop a monitoring and evaluation protocol.

The study forms part of a newly established collaboration between the Centre for Invasion Biology and the City of Cape Town Invasive Species Unit and is funded through the collaborative agreement between the Working for Water Program and the C·I·B. The project is suitable for students who are interested in invasion biology and who are happy to spend extended periods of time doing field work.

Key contacts

  • Dr Mirijam Gaertner, Centre for Invasion Biology (C·I·B) (gaertnem@sun.ac.za)
  • Dr Sjirk Geerts, Dept. Biodiversity & Conservation, Faculty of Applied Sciences, Cape Peninsula University of Technology (geertss@cput.ac.za)
  • Dr John Wilson, South African National Biodiversity Institute / Centre for Invasion Biology, Stellenbosch University (jrwilson@sun.ac.za)

Further reading

  • Geerts S, Botha PW, Visser V, Richardson DM, Wilson JRU. 2013. Montpellier broom (Genista monspessulana) and Spanish broom (Spartium junceum) in South Africa: An assessment of invasiveness and options for management. South African Journal of Botany 87: 134-145.
  • Kaplan H, Van Zyl HWF, Le Roux JJ, Richardson DM, Wilson JRU. 2012. Distribution and management of Acacia implexa (Benth.) in South Africa: A suitable target for eradication? South African Journal of Botany 83: 23-35.
  • Wilson, J. R. U., Ivey, P., Manyama, P. & Nänni, I. 2013. A new national unit for invasive species detection, assessment and eradication planning. South African Journal of Science, 109: 13 pages.
  • Zenni RD, Wilson JRU, Le Roux JJ, Richardson DM. 2009. Evaluating the invasiveness of Acacia paradoxa in South Africa. South African Journal of Botany 75: 485-496.

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Core Team Members: Mirijam Gaertner, Stellenbosch University

Level of project: MSc

Working title: Identification of priority areas for restoration

Background

Restoration is increasingly seen as vital when managing alien invasions since clearing of invasive species alone is often not sufficient for their long-term control, for reducing their ecosystem impacts, and for re-establishing native communities. However, active restoration is not always practical, nor is it always necessary. Research is required to develop methods for prioritizing areas, at different levels of spatial resolution, for different forms of mediation/restoration. Results from detailed restoration studies need to be synthesized to provide practical guidelines that can be used in planning.

This study will form part of a newly established research initiative of the City of Cape Town and will be based in the City. The main aim of the study is to prioritize species and areas for management and restoration and to provide management guidelines.

The study is funded through the collaborative agreement between the Working for Water Program and the C·I·B. The project is suitable for students who are interested in invasion biology and restoration ecology and who are happy to spend extended periods of time doing field work.

Key contacts

Further reading

  • Forsyth GG, Le Maitre DC, O'Farrell PJ, van Wilgen BW. 2012. The prioritisation of invasive alien plant control projects using a multi-criteria decision model informed by stakeholder input and spatial data. Journal of Environmental Management 103: 51-57.
  • Gaertner M, Holmes PM, Richardson DM. 2012. Biological invasions, resilience and restoration. Pages 265-280 in Andel J, Aronson J, eds. Restoration Ecology: The new frontier. Oxford: Wiley-Blackwell.
  • Holmes PM, Richardson DM. 1999. Protocols for the restoration based on recruitment dynamics, community structure and ecosystem function: Perspectives from South African fynbos. Restoration Ecology 7: 215-230.

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Core Team Members: Prof. Charles Griffiths, Department of Biological Sciences, UCT

Level of project: MSc or PhD

Working title: Ecological impacts of the white garden snail (Theba pisana)

Background

The invasive white garden snail occurs in a broad strip along the South African coastline from the northern Cape to about East London. The only local study to date (Odendall et al. 2008) examined its distribution and life history in the West Coast National Park, where densities reached 700 per m2 at some sites! Although these dense populations were observed to feed on a wide range of native plants no one has examined (1) impacts on plant diversity and standing biomass, (2) the wider implications of white garden snails as competitors to other herbivores, or (3) the implications of these snails as a food source for predators. Australian studies on Theba suggest that it can displace native snails, and Theba-infested plants are generally considered to be unpalatable to livestock.

Potential key questions

  • What are the impacts of Theba populations in the West Coast National Park on plant diversity and standing biomass? Manipulative field experiments can be used here.
  • What are the effects of Theba presence on herbivorous insects, small browsing antelope, and native snail species?
  • How important are Theba snails as a food resource for predators (birds, rodents, small carnivores) and how does their presence influence densities of predator populations?

Requirements

This project will involve a number of trips to the West Coast National Park and vicinity, where sampling and manipulative experiments will be conducted. The applicant should enjoy outdoor activities and working with invertebrates, have own transport, or at least a drivers licence, and be prepared to live for at least a few days at a time in the field.

Key contacts

Further reading

  • Baker, G.H. 1986. The biology and control of White snails (Mollusca: Helicidae), introduced pests in Australia. CSIRO Division of Entomology, Technical paper 24:1-31.
  • Baker, G.H. and Vogelzang, B.K. 1988. Life history, population dynamics and polymorphism of Theba pisana (Mollusca: Helicidae) in Australia. Journal of Applied Ecology 25: 867-887.
  • Odendaal L. J., T.M. Haupt and C.L. Griffiths 2008 The alien invasive land-snail, Theba pisana, in the West Coast National Park: is there cause for concern? Koedoe 50: 93-98.
  • Picker, M.D., C.L. Griffiths 2011. Alien and Invasive Animals — A South African Perspective. Randomhouse/Struik Cape Town 240pp.

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Core Team Members: Jaco Le Roux, Dave Richardson

Level of project: MSc, PhD or Postdoc

Working title: Biodiversity impacts of plant invasions — the role of mutualisms

Background

A major challenge to biodiversity conservation is quantifying and preventing the impacts of biological invasions. For example, how invasive species influence mutualistic interactions within communities they invade and its consequences for biodiversity remain essentially unknown. This research project aims to shed light on how, and to what extent, invasive legumes may alter the way native biodiversity interacts in the Cape Floristic Region (CFR).

The CFR is recognised as one of the most botanically diverse areas on the planet, being home to 9000 species. Two dominant plant families, Asteraceae (daisies) and Fabaceae (legumes), represent about 20% of the region’s species pool. Legumes are also over-represented among invasive plants in the CFR.

Landscapes dominated by invasive legumes must comprise altered native species-interactions, including mutualisms. A case in point involves one of the most fascinating and functionally critical plant-microbe mutualisms, that between legumes and soil bacteria known as rhizobia. Rhizobia are capable of entering roots and inducing the development of nodules where biological nitrogen fixation takes place. Organic forms of reduced atmospheric nitrogen produced by the bacteria can then be utilized by the host plant and ultimately enter the earth’s food webs. In exchange, bacterial symbionts acquire carbohydrates. Like many other interactions, rhizobial-legume mutualisms can be general or highly specific. The ability to fix nitrogen also contributes to the success of legumes as invasive species and, due to their relative abundance in invaded areas, can rapidly modify soil microbial communities. Community dominance by invasive legumes may lead to a decline in the relative abundance and even absence of certain native rhizobia and therefore nodulation failure in native legumes.

This project will aim to better understand changes in interaction networks between rhizobia and native CFR legumes in response to legume invasions. The project will utilize both genetic (DNA barcoding) and experimental work to determine the effects of altered mutualistic networks on native legume species performances.

Key contacts

  • Dr Jaco Le Roux t: 021 808 2086 e: jleroux@sun.ac.za
  • Prof Dave Richardson t: 021 808 3711

Further reading

  • Rodríguez-Echeverría S. et al. 2012. Differential effectiveness of novel and old legume-rhizobia mutualisms: implications for invasion by exotic legumes. Oecologia 170: 1–9.
  • Ndlovu, J. et al. (2013) Co-invasion of South African ecosystems by an Australian legume and its rhizobial symbionts. Journal of Biogeography DOI: 10.1111/jbi.12091

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Core Team Members: Jaco Le Roux, Dave Richardson, John Wilson

Level of project: MSc, PhD or Postdoc

Working title: Propagule pressure: The role of forestry plantations

Background

Understanding whether existing stands of commercially-important trees act as sources of invasive propagule pools is crucial for their effective management. Moreover, such information will promote the active involvement of forestry companies in seeking solutions to problems associated with invasive species. A project is envisaged to determine the importance of such commercial stands of Acacia and/or Pinus species in facilitating invasions. This project will use population genetics as a tool for improving our understanding of source-invasion dynamics and invasive spread at different spatial scales. For example, for invasive A. mearnsii in South Africa, initial results (Le Roux et al. 2011; Diversity Distrib., 17, 861-871) suggest that only a small number of genotypes are invasive despite the fact that many propagules are known to have been introduced from various Australian locations (and elsewhere in the world). The proposed project will assist in determining whether particular genotypes are always invasive even though many other genotypes are present. Alternatively it could be that commercial forestry and agroforestry have deliberately and artificially selected for only a few genotypes that are well suited to the South African environment (e.g. frost resistance, vigorous growth) and hence well-suited for invasiveness.

This project will aim to understand whether intentional plantings of alien species provide the source and foci for the initiation of invasions and whether commercial forestry is a major cause of important invasions in many parts of the world.

Key contacts

  • Dr Jaco Le Roux t: 021 808 2086 e: jleroux@sun.ac.za
  • Prof Dave Richardson t: 021 808 3711
  • Dr John Wilson t: 021 808 3408

Further reading

  • Thompson, G.D. et al. (2012) Cultivation shapes genetic novelty in a globally important invader. Molecular Ecology 21: 3187-3199.
  • Le Roux J.J. et al.(2011) Phylogeographic consequences of different introduction histories of invasive Australian Acacia species and Paraserianthes lophantha (Fabaceae) in South Africa. Diversity and Distributions 17: 861-871.

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Core Team Members: Jaco Le Roux, Dave Richardson

Level of project: PhD

Working title: The tale of two island endemics, Acacia koa and A. heterophylla

Background

Understanding the historic biogeographic processes that shaped current species distributions, and thus the evolution of different biotas, has become a central theme in ecology and is informative on how biodiversity is generated and maintained.

Truly puzzling and curious examples of biogeographic anomalies exist in nature. For example, the diverse genus Acacia Mill. (sensu stricto; previously grouped in Acacia subgenus Phyllodineae) consists of about 1012 species, most of them confined to Australia, with a few taxa found in south-east Asia and Oceania. Two particularly peculiar extra-Australian taxa are the closely-related island endemics Acacia koa A. Gray found in the Hawaiian Islands in the Pacific Ocean and A. heterophylla Willd. from La Réunion Island in the Indian Ocean. Not only is this geographic disparity truly remarkable, with ca. 18 000 km separating these two insular landmasses, but what makes it even more interesting is that these two species are considered each other’s closest living relatives. Recent work in our laboratory has illustrated that A. heterophylla from La Réunion Island represent a secondary colonization event from the Hawaiian Islands and is therefore the same species than A. koa. These two species represent one of the most astonishing examples of long-distance dispersal.

This project will aim to better understand and compare the ecology of these two island endemics by studying their ecological requirements and interactions with other biota in their native ranges (Hawaii and La Réunion Island). This research will shed light on how quickly speciation can happen and to what extent geographic isolation can shape evolutionary trajectories.

Key contacts

  • Dr Jaco Le Roux t: 021 808 2086 e: jleroux@sun.ac.za
  • Prof Dave Richardson t: 021 808 3711

Further reading

  • Brown et al. (2012) Phylogenetic connections of phyllodinous species of Acacia outside Australia are explained by geological history and human-mediated dispersal. Australian Systematic Botany 25, 390–403.

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Core Team Members: Cang Hui

Level of project: PhD or Post-Doc

Working title: The architecture of pollination and seed-dispersal networks of Australian acacias

Background

The reciprocal dependence of plants on their pollinators and seed dispersers is widespread in nature. This mutualistic dependence can enhance seed production and establishment and reduce inbreeding genetic load of the plants, with only limited carbohydrate loss as nectar and seed to the pollinators and consumers. It is thus an efficient way to improve the fitness and survival potential of both partners. These mutualistic interactions further contribute to weaving a complex web in ecosystems, and are important for maintaining ecosystem stability, resilience and functioning. Invasion of Australian acacia species can cause important effects on the native mutualistic communities in South African ecosystems. For example, recent work has shown that Acacia saligna can potentially have profound implications for native plants that share pollinators with the invader. Invasion of generalist species can potentially trigger a cascade effect in the network and significantly alter how it functions. Research is needed to provide further quantification of the influence of selected Australian acacias on mutualistic networks in South African ecosystems. Native communities of plants, pollinators and seed dispersers invaded by different Australian acacias at different levels (measured by coverage) will be surveyed to construct network connectivity matrices for further analysis.

Key contacts

Further reading

  • Bascompte et al. (2003) PNAS, 100, 9383-9387
  • Thebault & Fontaine (2010) Science, 329, 853-866
  • Zhang et al. (2011) Ecol. Lett., 14, 797-803

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Core Team Members: Cang Hui and John Wilson

Level of project: MSc or Post-Doc

Working title: From snapshots of species distribution to landscape-scale dynamics of invasive plants

Background

Early detection often records introduced plant species as snapshots of presence points through remote sensing or ground surveys. This provides valuable, but rather limited information on the current status of the focal species in a novel environment. However, point-based maps seldom provide sufficient evidence on which to base management decisions, especially in highly heterogeneous landscapes. It is of great value to elucidate the interrelationships between the spatial structure of founding populations, landscape heterogeneity, and the invasion potential of the focal species. This is a rapidly growing field of research. This project is envisaged to design spatial indices and analytical models for forecasting spread rates for selected species using point maps collected from the various sources, including the EDRR programme, NRMP teams, conservation agencies, and from the literature. This will benefit EDRR and conservation agencies in providing for the formulation of management plans.

Key contacts

Further reading

  • Hui (2011) Ecological Modelling 222, 442-446
  • Eppinga et al. (2010) 95th ESA Annual Meeting, PS 96-65
  • Dennis et al. (2011) Biol. Invasions, 13, 401-411

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Core Team Members: Cang Hui

Level of project: PhD or Post-Doc

Working title: Seed dispersal and spread potential of invasive Australian acacias

Background

Understanding species ranges and dynamics is among the main pursuits in ecology and biogeography. Spread of invasive species, while posing real and escalating threats to biodiversity conservation and ecosystem functioning, provides a superb natural experiment for unraveling the mechanisms and factors behind the dynamics of species’ geographic ranges. Generally, a species’ dispersal strategy can be depicted by its dispersal kernel. It is evident that dispersal strategy is an important determinant of both the range and dynamics of invasive species. Better to monitor the distribution and assess the risk of invasive plants, it is crucial to estimate the capacity of seed dispersal capacities of focal species, from which spread potential can be estimated. Many Australian acacias have evolved multiple dispersal strategies and polymorphic seeds. This project is envisaged to quantify the diffusion rates of different seed morphs for selected Acacia species. The proportion of different dispersal strategies (morphs) will be estimated for populations at different localities across the entire invaded range. Adaptive dynamics will be used to explore the rise of multiple dispersal strategies and seed morphs.

Key contacts

Further reading

  • Hui et al., 2010; In: Fifty Years of Invasion Ecology: The Legacy of Charles Elton [ed. by D.M. Richardson]. Wiley-Blackwell, Oxford
  • Davidson & Morton 1984; Ecology 65, 1038-1051
  • Whitney & Stanton 2004; Ecology 85, 2153-2160

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Core Team Members: Susana Clusella-Trullas

Level of project: MSc

Working title: Identifying key species characteristics underpinning successful invasion of the ladybird Cryptolaemus montrouzeri: a multidisciplinary approach

Background

To improve the understanding of mechanisms underlying biological invasion, we can investigate differences between native and invasive populations through building distribution models and measuring physiological traits (Rey et al. 2012; Hill et al. 2013). Insects provide some of the best study organisms to investigate biological invasions due to their abundance and established experimental protocols.

Cryptolaemus montrouzeri (Cryptolaemus) is a ladybird native to Australia, used as a biocontrol agent for mealybugs and scale insects in orchards and vineyards. The species was first taken as a biocontrol agent to California in 1891 and is now found in ~50 countries, including South Africa (Solangi et al. 2013). The varied introduction pathways and global distribution of Cryptoleamus provide a unique opportunity to understand functional trait variation between populations and the influence of local conditions on these traits. By characterizing traits of C. montrouzeri in South Africa, comparisons to its native range data in Australia and to introduced populations in California can be made.

The main component of this project will be to build distribution models based on environmental data, occurrence data and physiological information. The project will incorporate field work to collect a number of populations of C. montrouzeri across South Africa and laboratory work to characterize ecophysiological profiles of the species. The combination of physiological data and distribution modeling techniques should highlight potential limits to the species distribution, gain insight into potential eco-evolutionary mechanisms underpinning biological invasions, and provide a comparison study to other invasive ladybirds, such as Harmonia axyridis.

Further reading

  • Hill MP, Chown SL, Hoffmann AA (2013) A predicted niche shift corresponds with increased thermal resistance in an invasive mite, Halotydeus destructor. Global Ecology and Biogeography 22: 942-951.
  • Rey O, et al. (2012) Where do adaptive shifts occur during invasion? A multidisciplinary approach to unravelling cold adaptation in a tropical ant species Invading the Mediterranean area. Ecology Letters 15: 1266-1275.
  • Solangi et al. (2013) Effect of high temperatures on survival and longevity of the predator Cryptolaemus montrouzeri. Phytoparasitica 41: 213-219.

Key contacts

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Core Team Members: John Wilson, Dave Richardson

Level of project: MSc

Working title: Bamboo cultivation in South Africa – an assessment of the potential impacts and developing guidelines for cultivation best practices

Background

Bamboos are widely cultivated around the world for horticultural purposes, as building material, and recently, for CO2-mitigation projects. In South Africa, bamboos have been planted as ornamental plants for many years, but only in the last few years there has been an upsurge in interest in developing bamboo plantations for their other potential uses, and also as part of social upliftment projects. However, a number of bamboo species (e.g. Bambusa balcoa and Bambusa vulgaris) are problematic species elsewhere in the world, but little is known about the potential for bamboos to become invasive in South Africa, or even whether bamboos are already naturalizing.

The purpose of the studentship would be to:

  • Identify the species that are cultivated in South Africa, particularly those that are proposed to be, or already grown, in large-scale plantations;
  • Compile a database of all known bamboo plantations;
  • Locate naturalizing populations of bamboos;
  • Perform a risk assessment analysis on all bamboos currently growing in South Africa, and also those species that are proposed for introduction;
  • Develop guidelines for the cultivation of bamboos that will prevent naturalization.

The student should be prepared to (a) write at least two papers for publication in a top international journal, and (b) develop guidelines for SANBI's Invasive Species Programme for the management of bamboos and their introductions in South Africa.

This is a project suitable for students interested in social aspects of invasion biology, risk assessment, alien plant management, GIS and modelling.

The project will be embedded in an extensive research program on Integrated management of invasive alien species in South Africa and is funded through the collaborative agreement between the Working for Water Program and the C·I·B.

Further reading

  • Blanchard, R., Richardson, D.M., O’Farrell, P.J., von Maltitz, G.P. (2011) Biofuels and biodiversity in South Africa. South African Journal of Science 107: 19-26.
  • Kumschick, S., Richardson, D.M. (2013) Species-based risk assessments for biological invasions: advances and challenges. Diversity and Distributions 19: 1095-1105
  • http://www.trees.co.za/bamboo-for-africa/

Key contacts

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Core Team Members: Dave Richardson, John Wilson, Jaco Le Roux

Level of project: MSc or PhD

Working title: The invasion ecology of fleshy-fruited Myrtaceae, with special emphasis on South Africa

Background

Thousands of tree species have been moved around the world by humans in the past few centuries, and hundreds of these are now invasive in different parts of the world. Our understanding of what makes some species invasive is imperfect and much more work is needed to develop tools for the accurate screening of invasiveness in different groups.

Recent research at the Centre for Invasion Biology has resulted in major advances in understanding of the invasion ecology of key tree genera such as Acacia, Eucalyptus, Pinus and Prosopis. Information from this research has already been useful for management.

Much less work has been done on the ecology of fleshy-fruited invasive tree species in South Africa, several species of which are important invaders. Following on the approach taken in previous work on tree invasions, the plan is to identify other key groups for detailed study. One group with many species that are widely planted outside their native ranges and for which increasing problems with invasiveness are emerged is the group of fleshy-fruited species in the family Myrtaceae.

At least seven genera of fleshy-fruited Myrtaceae feature in the global list of invasive trees and shrubs: Eugenia (E. brasiliensis, E. uniflora), Pimenta (P. dioica); Psidium (P. cattleianum, P. guajava, P. guineense, and hybrids of last mentioned), Rhodomyrtus (R. tomentosa), Syzygium (S. australe, S. cumini, S. jambos, S. malaccense, S. paniculatum), Ugni (U. molinae) and Waterhousea (W. floribunda).

The proposed study will involve the following aspects:

  • A review of the ecology of fleshy-fruited species in the family Myrtaceae;
  • A global review of the movement of species in the group around the world, evidence for naturalization and invasiveness and impacts in invaded ecosystems, and control efforts;
  • Detailed studies of the invasion ecology of selected species in South Africa (Syzygium paniculatum is a strong candidate for such a study);
  • Development of a synthesis of the distribution of species in this group in South Africa and a strategy for their integrated management (including a framework for assessing the risk of invasiveness in the group).

Good opportunities exist for applying molecular techniques to explore facets of the ecology of selected taxa.

The project will be embedded in an extensive research program on Integrated management of invasive alien species in South Africa and is funded through the collaborative agreement between the Working for Water Program and the C·I·B.

Further reading

  • Milton, S.J., Wilson, J.R.U., Richardson, D.M., Seymour, C.L., Dean, W.R.J., Iponga, D.M. & Procheş, Ş. (2007). Invasive alien plants infiltrate bird-mediated shrub nucleation processes in arid savanna. Journal of Ecology 95: 648-661.
  • Rejmánek, M. & Richardson, D.M. (2013). Trees and shrubs as invasive alien species – 2013 update of the global database. Diversity and Distributions 19: 1093-1094.
  • Richardson, D.M. & Rejmánek, M. (2011) Trees and shrubs as invasive alien species – a global review. Diversity and Distributions 17: 788-809.

Key contacts

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Core Team Members: Prof. David M. Richardson, Dr John R. Wilson, Dr Johannes J. Le Roux

Level of project: MSc

Working title: An assessment of the extent of invasion and genetic structure of Eucalyptus camaldulensis in South Africa

Background

Thousands of species of trees have been moved around the world by humans for many reasons. Hundreds of species are now invasive in areas outside their native ranges. These species cause many types of impacts.

Good progress has been made towards understanding of the determinants of invasiveness of tree species. Such information is required to improve our ability to screen new introductions to determine the risks of invasiveness. Despite the advances in understanding, many questions remain unanswered in tree invasion ecology. One conundrum is why Eucalyptus species have fared so poorly as invasive species around the world. Many species have been very widely planted around the world, but only a few species are clearly invasive, and overall levels of invasion are much lower than for instance pines (genus Pinus), many species of which have enjoyed similar levels of planting around the world as eucalypts.

Eucalyptus camaldulensis (the river red gum) is the most widespread invasive eucalypt in South Africa. In the Western Cape, the species has invaded hundreds of kilometres of riparian vegetation where dense stands cause major impacts on hydrology and other ecosystems functions.

Research is required to determine the extent of invasion of this species throughout South Africa, and patterns and processes associated with invasion, in order to determine the potential of the species to spread further. Several subspecies of the species have been described in Australia, but nothing is known of the genetic structure of the species in South Africa (or in other parts of the world where the species is also an emerging invader). A study of the genetics of the species in South Africa is needed to help understand the introduction and invasion history of the species.

Insights on the invasion ecology of this species will also be useful to help us understand the potential for other species of the family Myrtaceae to invade.

The project will be embedded in an extensive research program on Integrated management of invasive alien species in South Africa and is funded through the collaborative agreement between the Working for Water Program and the C·I·B.

Further reading

  • Forsyth, G.G., Richardson, D.M., Brown, P.J. & van Wilgen, B.W. (2004). A rapid assessment of the invasive status of Eucalyptus species in two South African provinces. South African Journal of Science 100: 75-77.
  • Rejmánek, M. & Richardson, D.M. (2011). Eucalypts. In: Simberloff, D. & Rejmánek, M. (eds). Encyclopedia of biological invasions, pp. 203-209. University of California Press, Berkeley. ISBN 978-0-520-26421-2.
  • Richardson, D.M. & Rejmánek, M. (2011) Trees and shrubs as invasive alien species – a global review. Diversity and Distributions 17: 788-809.
  • Tererai, F., Gaertner, M., Jacobs, S.M. & Richardson, D.M. (2013). Eucalyptus invasions in riparian forests: Effects on native vegetation community diversity, stand structure and composition. Forest Ecology and Management 297: 84–93.

Key contacts

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Core Team Members: John Wilson, Dave Richardson

Level of project: Honours or MSc

Working title: Risk assessment of introduced alien grasses in South Africa

Background

Alien grasses have major impacts in many countries around the world, often causing drastic changes to fire regimes, and thereby, completely altering plant communities and vegetation structure. In South Africa, grasses seemingly have had little impact on ecosystems, but this lack of an observed impact may largely be due to the fact that this group of plants has received so little attention from invasion biologists and invasive-plant managers in the country. The last in-depth review of alien grasses in South Africa identified at least 146 naturalized species, but this was conducted almost a decade ago, and preliminary investigations of online data sources suggests that there may be more than 300 alien grass species that have successfully naturalized.

The purpose of the studentship would be to conduct risk assessments for alien grass species introduced into South Africa in order to prioritize management of these species. This will include:

  • Using a modified version of the Australian Weed Risk Assessment to score introduced species;
  • Modelling the potential distributions of these species;
  • Determining whether introduced species are problematic elsewhere in the world;
  • Investigating the literature to determine potential impacts of these species.

This project will result in (a) at least one publication in a top international journal, and (b) will contribute directly to the operations of the SANBI's Invasive Species Programme by influencing management priorities of alien grasses in South Africa.

This is a project suitable for students interested in risk assessment, alien plant management, GIS and modelling.

The project will be embedded in an extensive research program on Integrated management of invasive alien species in South Africa and is funded through the collaborative agreement between the Working for Water Program and the C·I·B.

Further reading

  • D’Antonio, C.M., Vitousek, P.M. (1992) Biological invasions by exotic grasses, the grass/fire cycle, and global change. American Naturalist 23: 63-87.
  • Kumschick, S., Richardson, D.M. (2013) Species-based risk assessments for biological invasions: advances and challenges. Diversity and Distributions 19: 1095-1105 DOI: 10.1111/ddi.12110
  • Milton, S.J. (2004) Grasses as invasive alien plants in South Africa. South African Journal of Science 100: 69-75.
  • Musil, C.F., Milton, S.J., Davis, G.W. (2005) The threat of alien invasive grasses to lowland Cape floral diversity: an empirical appraisal of the effectiveness of practical control strategies. South African Journal of Science 101: 337-344.

Key contacts

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